Air Compressor Applications
Compressed-air power tools can dramatically decrease the amount of time spent on a project. Many homeowners and DIY'ers will use smaller, portable units (either hand-carried or wheeled) that move easily from the garage to the house, yard or roof. Common air tools such as brad and finish nailers, drills, and impact wrenches require about 0–5 CFM (Cubic feet per minute — units in which air flow is measured). It's important to know if the air compressor you purchase will drive the air tool you'll need for your project. For example, smaller air nailers run on 2 to 5 CFM at 70 to 90 PSI, while larger grinders, sanders and polishers require up to 10 or more CFM and 100 to 120 PSI.
Commercial Compressors and Garage Compressors
Air compressors used for business/professional/commercial applications are often classified “industrial grade.” They're packed with features that let you take on more demanding jobs with more horsepower, more CFM, more PSI and longer run times. Though some commercial compressors are portable, many are stationary units with large-capacity, ASME certified air tanks (up to 120 gallons), greater HP, more CFM air volume and faster recovery time to run a wide variety of air tools for as long as you need them to do the job.
Determine Your CFM Requirements
The chart below includes some common air tools and their average CFM measurements. Reference this chart to determine what continuous CFM rating is required of your air compressor. Air tools are often rated as “Average CFM.” “Average CFM” is typically based on a 25% duty cycle (15 seconds out of a min.). This sometimes creates a problem with tools that are used on a continuous basis (ex. orbital sanders, die grinders, etc). Nailers and impact wrenches typically don't have the same problem since by their nature are used more intermittently.
If you plan on using an air tool on a continuous basis, it is a good idea to multiply the “Average CFM” x 4 to get a continuous CFM rating for the tool.
Two-Stage versus Single-Stage
Single-Stage compressors have one piston that compresses and delivers air to the storage tank. The single-stage system is normally found on light-duty compressors with a maximum rating below 150 pounds of pressure per square inch (psi). Single-stage compressors are adequate for most home users.
Two-Stage compressors have two pistons that compress and deliver air to the storage tank. The first piston compresses the air and pushes it through a check valve to the second piston. The second piston further compresses the air and delivers it to the storage tank. The two-stage system is usually found on commercial heavy-duty compressors with maximum ratings above 150 psi. Two-stage compressors are good choices for continuous use or shop environments.
Things to Consider
Horsepower Ratings are a measure of the horsepower (HP) the compressor motor produces. Compressor motors generally range from 1.5 HP to 6.5 HP. More powerful units are available for industrial applications. Usually higher horsepower motors yield greater psi and are capable of carrying a heavier workload.
Compressor Storage Tanks are rated in gallons. Larger tanks store more compressed air at higher pressures. The amount of air a compressor delivers is measured in cubic feet per minute (CFM). Note that the CFM a compressor delivers changes at varying psi. Most air tools have specific requirements for volume and pressure. These requirements must be met for the tool to function properly. When choosing a compressor, consider the tools you want it to operate. Select the tool that requires the highest CFM at the highest psi, and add 50% to the required CFM for a margin of safety. For example, if a tool requires 3 CFM at 90 psi, select a compressor that delivers at least 4.5 CFM at 90 psi. Use this formula to ensure that the tool receives enough air to function properly.
Oil-Free Compressors have sealed bearings and require less maintenance than oil-lubricated compressors. Oil-free compressors have plenty of power for most noncommercial uses.
Oil-Lubricated Compressors require the user to change the oil regularly. (Consult the owner's manual for specific intervals). Most industrial compressors are oil-lubricated.
Electric-Powered Compressors are the most common and are easy to use in any area with a ready electrical supply.
Gas-Powered Air Compressors are a good choice for areas where electricity is limited or unavailable. Don't use gas-powered compressors in confined or unventilated areas.